Medical device incorporating a polymer blend

ABSTRACT

A catheter including a catheter shaft formed from a polymer blend and/or a braid. The polymer blend may include polyoxymethylene added in the dispersion phase to a polymer blend. The catheter braid can be formed from at least two continuous wires that are woven together. The catheter braid can include a proximal braid section and a distal braid section. Each of the continuous wires has a proximal diameter corresponding to the proximal braid section and a distal diameter corresponding to the distal braid section. The distal diameter of each wire can be less than the proximal diameter of that wire. A catheter braid so formed can be included in a catheter.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 10/645,764, filed Aug. 20, 2003 and entitledCATHETER WITH THIN-WALLED BRAID, the entire disclosure of which isherein incorporated by reference.

TECHNICAL FIELD

The invention relates generally to elongate medical devices and moreparticularly to catheters and catheter shafts that include improvedpolymer blends and/or braided or other reinforcement elements.

BACKGROUND OF THE INVENTION

Reinforcing layers such as reinforcing braid layers can providethin-walled catheters with desired resistance to kinking while retainingdesirable flexibility. In some instances, it can be desirable forportions of a thin-walled catheter to be either more flexible or lessflexible than other portions of the catheter. In particular, it can bedesirable for a distal portion of a catheter to be more flexible,especially if the distal portion of the catheter is curved. However, areinforcing braid layer that can provide suitable kink resistance inother portions of a catheter may not provide sufficient flexibility inthe distal portion of the catheter.

A need remains for improved catheters having desirable kink resistancewhile being sufficiently flexible, particularly in distal portions thatcan be curved in use, especially when tracking dramatic bends in thevasculature of an individual.

SUMMARY OF THE INVENTION

The present invention is directed to catheters, catheter shafts, andmethods for making and using the same. In some embodiments, thecatheters may include a polymer blend. For example, the blend mayinclude polyoxymethylene added in the dispersion phase to a polymerblend.

The catheters and catheter shafts can also include a braid that can bewoven from continuous wires in some embodiments. A portion of each wirecan have a diameter that is reduced with respect to another portion ofthat wire. Accordingly, an exemplary embodiment of the invention can befound in a catheter braid that is formed from at least two continuouswires that are woven together. The catheter braid can include a proximalbraid section in which each of the continuous wires have a proximaldiameter, and a distal braid section in which each of the continuouswires have a distal diameter. For each continuous wire, in one preferredembodiment, the distal diameter of the continuous wire is less than theproximal diameter of the continuous wire.

Another example embodiment of the invention can be found in a catheterthat has a distal end and a proximal end, and a distal region that isproximate the distal end. The catheter can include an inner layer thatextends from the distal end to the proximal end, and a reinforcing braidlayer that can be disposed over the inner layer. The braid layer can beformed from at least two continuous wires that are woven together. Thebraid layer can have a proximal braid section in which each of thecontinuous wires has a proximal diameter, and a distal braid section inwhich each of the continuous wires has a distal diameter. The distaldiameter of each continuous wire, in one preferred embodiment, is lessthan the proximal diameter of each continuous wire.

An example embodiment of the invention can also be found in a method offorming a catheter that has a distal end and a proximal end. Thecatheter can include an inner layer and a braid layer. The catheter canbe formed by weaving together at least two continuous wires to form thebraid layer. The formed braid layer distal portion is then, in apreferred embodiment, immersed in an etching solution to thin the wiresto a desired reduced diameter. The resulting braid layer has a proximalsection in which each of the wires has a proximal diameter and a distalsection in which each of the wires has a distal diameter that is lessthan the proximal diameter. The braid layer, once formed, can bepositioned over the inner layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a catheter in accordance with an embodiment ofthe invention;

FIG. 2 is a cross-sectional view of the catheter of FIG. 1 taken alongline 2-2;

FIG. 3 is a partially sectioned view of the catheter of FIG. 1;

FIG. 4 is a partially sectioned cutaway view of a portion of a wovenbraid in accordance with an embodiment of the invention;

FIG. 5 is a partially-sectioned view of a portion of a woven braid inaccordance with an embodiment of the invention; and

FIG. 6 is a partially sectioned view of a distal portion of the catheterof FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

The following description should be read with reference to the drawingswherein like reference numerals indicate like elements throughout theseveral views. The drawings, which are not necessarily to scale, depictillustrative embodiments of the claimed invention.

FIG. 1 is a plan view of a catheter 10 in accordance with an embodimentof the invention. The catheter 10 can be any of a variety of differentcatheters. In some embodiments, the catheter 10 can be an intravascularcatheter. Examples of intravascular catheters include balloon catheters,atherectomy catheters, drug delivery catheters, diagnostic catheters andguide catheters. The intravascular catheter 10 can be sized inaccordance with its intended use. The catheter 10 can have a length thatis in the range of about 50 to about 150 centimeters, preferably in therange of about 100 to about 150 centimeters, and can have any usefuldiameter. As illustrated, FIG. 1 portrays a guide catheter, but theinvention is not limited to such. Preferred methods of manufacture aredescribed herein. The catheter 10 can also be manufactured usingconventional techniques.

In the illustrated embodiment, the intravascular catheter 10 includes anelongate shaft 12 that has a proximal end 14 and a distal end 16. A huband strain relief assembly 18 can be connected to the proximal end 14 ofthe elongate shaft 12. The hub and strain relief assembly 18 includes amain body portion 20, and a strain relief 24 that is intended to reducekinking. The hub can also include a pair of flanges 22. The hub andstrain relief assembly 18 can be of conventional design and can beattached using conventional techniques.

The elongate shaft 12 can include one or more shaft segments havingvarying degrees of flexibility. As illustrated, the elongate shaft 12includes a first shaft segment 26, a second shaft segment 28 and a thirdshaft segment 30. In some embodiments, the elongate shaft 12 can includefewer shaft segments or only one shaft segment or can include more thanthree segments, depending on the flexibility requirements of aparticular application.

FIG. 2 is a cross-sectional view of the elongate shaft 12, taken alongthe line 2-2 of FIG. 1, while FIG. 3 is a longitudinal cross-sectionalview of a portion of the elongate shaft 12. The proximal portions of theelongate shaft 12, as illustrated, include an outer layer 34 and aninner layer 36, and can include a reinforcement layer 38 that ispositioned between the inner layer 36 and the outer layer 34. The innerlayer 36 defines a lumen 40 that extends through the elongate shaft 12.The distal portion 32 of the elongate shaft 12 will be discussed ingreater detail hereinafter.

Each of the shaft segments 26, 28, 30 can have a similar construction.In particular, each of the shaft segments 26, 28, 30 can include aninner layer 36, a reinforcing layer 38 that is the same for orcontinuous through each of the shaft segments 26, 28, 30 and an outerlayer 34 that becomes more flexible in the shaft segments 26, 28, 30closest to the distal end 16 of the catheter 10. For example, theproximal shaft segment 26 can have an outer layer that is formed from apolymer having a hardness of 72D (Durometer), the intermediate shaftsegment 28 can have an outer layer having a hardness of 68D and thedistal shaft segment 30 can have an outer layer having a hardness of46D.

Each of the shaft segments 26, 28, 30 can be sized in accordance withthe intended function of the resulting catheter 10. For example, theshaft segment 26 can have a length of about 35 inches, the shaft segment28 can have a length in the range of about 2 to 3 inches and the shaftsegment 30 can have a length in the range of about 1 to 1.25 inches.

The shaft segments 26, 28, 30 can be formed of any suitable materialsuch as a polymeric material. Some examples of suitable polymers mayinclude polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene(ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane, polypropylene (PP), polyvinylchloride (PVC),polyether-ester (for example, ARNITEL® available from DSM EngineeringPlastics), ether or ester based copolymers (for example,butylene/poly(alkylene ether) phthalate and/or polyester elastomers suchas HYTREL® available from DuPont), polyamide (for example, DURETHAN®available from Bayer or CRISTAMID® available from Elf Atochem),elastomeric polyamides, block polyamide/ethers, polyether block amide(PEBA, for example available under the trade name PEBAX®, silicones,polyethylene (PE), Marlex high-density polyethylene, Marlex low-densitypolyethylene, linear low density polyethylene (for example REXELL®,polyester, polybutylene terephthalate (PBT), polyethylene terephthalate(PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN),polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI),polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyparaphenylene terephthalamide (for example, KEVLAR®), polysulfone,nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon),perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin,polystyrene, epoxy, polyvinylidene chloride (PVdC), polycarbonates,ionomers, biocompatible polymers, other suitable materials, or mixtures,combinations, copolymers thereof, polymer/metal composites, and thelike. In some embodiments, any one or all of shaft segments 26, 28, 30can be blended with a liquid crystal polymer (LCP). For example, themixture can contain up to about 6% LCP. This has been found to enhancetorqueability.

In these and some other embodiments, any one or all of shaft segments26, 28, 30 can include polymer blends. Some examples of suitable polymerblends include PBT and polyether-ester blends (e.g., PBT/ARNITEL®), PBTand ether or ester based copolymer blends (e.g., PBT/HYTREL® blends),POM combined with a PBT and polyether-ester blend (e.g., DELRIN®, PBT,and ARNITEL®), POM combined with a PBT and ether or ester basedcopolymer blend (e.g., DELRIN®, PBT, and HYTREL® blends), otherpolyesters (such as polyethylene terephthalate (PET), polytrimethyleneterephthalate, polyethylene naphthalate (PEN)) blended withpolyether-ester, other polyesters blended with ether or ester basedcopolymer, POM combined with other polyesters blended withpolyether-ester, POM combined with other polyesters blended with etheror ester based copolymer, polyurethane and POM blends, and the like orany other suitable blend. In general, as the amount of POM addedincreases, the strength of the resultant blend increases. Some examplevolume percents for blends including POM, PBT, and ether or ester basedcopolymer such as HYTREL® (or a polyether-ester such as ARNITEL®)suitable for making any one or all of the shaft segments 26, 28, 30 arelisted in Table 1 below.

TABLE 1 ether or ester based copolymer (e.g., HYTREL ®) or POM PBTpolyether-ester (e.g., ARNITEL ®)  5% 55% 40% 10% 50% 40% 20% 40% 40%30% 30% 40% 40% 20% 40% 30% 40% 30% 30% 50% 20% 30% 60% 10%Other volume percents are contemplated. For example, some blends mayinclude about 5% to about 90% PBT or about 5% to about 90% ether orester based copolymer (e.g., HYTREL®) or polyether-ester (e.g.,ARNITEL®).

Polymer blends such as PBT/polyether-ester and PBT/ether or ester basedcopolymer (for example, PBT/ARNITEL® and PBT/HYTREL®) are useful formaking catheter shafts such as shaft 12 as well as any other medicaldevice that includes a polymeric structure. One reason that these blendsare desirable is because of its ease in manufacturing, for example,processes such as extrusion. Adding POM to these blends may be desirablebecause the POM allows for stronger yet more flexible shafts to bemanufactured due to the properties of POM. Typical POM blends, however,are not as easy to extrude as PBT/ARNITEL® and PBT/HYTREL®. It has beendetermined that adding POM in the dispersion phase to PBT/ARNITEL® orPBT/HYTREL® blends allows shafts to be manufactured (e.g., shaft 12)that have the desirable characteristics of POM (e.g., strength andflexibility) while still having the ease in manufacturing ofPBT/ARNITEL® or PBT/HYTREL® blends. Accordingly, using a blend thatcombines POM in the dispersion phase with a PBT/ARNITEL® or PBT/HYTREL®blend allows shaft 12 to be manufactured with the desired amount ofstrength and flexibility, even when shaft 12 has a relatively lowprofile, is thin-walled, or otherwise reduced in size.

Dispersing or otherwise adding POM in the dispersion phase is understoodto be dispersing POM in a molten PBT/ARNITEL® or PBT/HYTREL® blend.Alternatively, all three materials (i.e., POM/PBT/ARNITEL® orPOM/PBT/HYTREL®) can be melted at the same time. Because adding POM inthe dispersion phase will occur at temperature where the PBT/ARNITEL® orPBT/HYTREL® blend is melted and because the melting temperature ofPBT/ARNITEL® and PBT/HYTREL® blends are higher than POM, the POM willalso melt when added in the dispersion phase. However, the POM will notmix with the PBT/ARNITEL® or PBT/HYTREL® blend. Instead, the particlesof molten POM will disperse in the melted PBT/ARNITEL® or PBT/HYTREL®blend. In a sense, the dispersion phase POM together with PBT/ARNITEL®or PBT/HYTREL® blend would be similar in appearance to an oil and watermix (i.e, the POM being akin to the “oil” and the PBT/ARNITEL® orPBT/HYTREL® blend being akin to the “water”). It should be noted thatthe amount of POM that can be added in the dispersion phase appears tobe limited. For example, blends with about 50% or more POM tend to notdisperse as well in PBT/ARNITEL® or PBT/HYTREL® blends. In someinstances, increasing the amount of POM can result in the oppositephenomenon, i.e., the PBT/ARNITEL® or PBT/HYTREL® blend “dispersed” inthe POM.

In some embodiments, adding POM in the dispersion phase may occur priorto or during an extrusion process, for example, an extrusion processsuitable for manufacturing shaft 12, any or all of shaft segments26/28/30, or any other portion of catheter 10. Thus, the moltenPBT/ARNITEL® or PBT/HYTREL® blend having POM added in the dispersionphase would be extruded to form shaft 12 or any of segments 26, 28, 30.As stated above, the POM will not directly mix with the PBT/ARNITEL® orPBT/HYTREL® blend when dispersed or combined in the dispersion phase.Instead, the POM will remain as a series of particles or dropletsdispersed in the PBT/ARNITEL® or PBT/HYTREL® blend. Moreover, theresultant shaft 12 will have a material composition where the POMremains dispersed in the PBT/ARNITEL® or PBT/HYTREL® blend.

Adding POM in the dispersion phase may be desirable for a number ofreasons. For example, adding POM in the dispersion phase to thePBT/ARNITEL® or PBT/HYTREL® blend allows for greater flexibility interms of adjusting the performance of the resultant shafts 12. This maymake it easier, for example, to adjust the amounts of POM in the polymerblend than if the POM was blended in some other manner. In addition, byadding POM in the dispersion phase together with the PBT/ARNITEL® orPBT/HYTREL® blend, the combination is more easily extruded than otherpolymer blends that include POM not in the dispersion phase. These samedesirable characteristics can also be realized with other combinationsof dispersion phase POM and polymer blends including any of thosecombinations listed above. For example, dispersion phase POM can beadded to PBT/ARNITEL® or PBT/HYTREL® blend.

Once the shaft 12 or shaft segments 26, 28, 30 are extruded, they may besubjected to one or more curving processes and/or other processes thatinclude heating typically used in catheter 10 manufacturing. The curvingprocesses may include disposing shaft 12 in a mold corresponding to thedesired final curve and then heating. In some embodiments, the heatingmay occur at a temperature at or near the highest temperature possiblethat will not melt the PBT/ARNITEL® or PBT/HYTREL® blend. For example,the heating may take place at a temperature higher than the meltingpoint of POM but lower than the melting point of the PBT/ARNITEL® orPBT/HYTREL® blend. However, a number of other temperatures andmanufacturing conditions are contemplated and known in the art.

In some embodiments, the inner layer 36 can be a single piece uniformmaterial extending over the length of the shaft 12 and can define alumen 40 that can run the entire length of the elongate shaft 12 andthat is in fluid communication with a lumen (not illustrated) extendingthrough the hub assembly 18. The lumen 40 defined by the inner layer 36can provide passage to a variety of different medical devices or fluids,and thus the inner layer 36 can be manufactured from or include alubricious material to reduce friction within the lumen 40. Examples ofsuitable materials include polytetrafluoroethylene (PTFE), such asTEFLON®. The inner layer 36 can be dimensioned to define a lumen 40having an appropriate inner diameter to accommodate its intended use. Insome embodiments, the inner layer 36 can define a lumen 40 having adiameter in the range of about 0.04 to about 0.10 inches and can have awall thickness of about 0.001 to about 0.02 inches.

In some embodiments, the outer layer 34 can include a portion made froma thermoplastic polymer such as a co-polyester thermoplastic polymersuch as that available commercially under the ARNITEL® name. The use ofan ARNITEL® polymer is described in detail below. The outer layer 34 canhave an inner diameter that is about equal to the outer diameter of theinner layer 36. The outer layer 34 can have an inner diameter that isslightly greater than the outer diameter of the inner layer 36 toaccommodate the thickness of the reinforcing braid layer 38. In someembodiments, the outer layer 34 can have an inner diameter in the rangeof about 0.0600 to about 0.0618 inches and an outer diameter in therange of about 0.0675 to about 0.0690 inches.

In some embodiments, the outer layer 34 or portions thereof can includeor be filled with a radiopaque material to make the outer layer 34 orportions thereof more visible when using certain imaging techniques, forexample, fluoroscopy techniques. Any suitable radiopaque material knownin the art can be used. Some examples include precious metals, tungsten,barium subcarbonate powder, and the like, and mixtures thereof. In someembodiments, the polymer can include different sections having differentamounts of loading with radiopaque material. For example, the outerlayer 34 can include a distal section having a higher level ofradiopaque material loading, and a proximal section having acorrespondingly lower level of loading.

A reinforcing braid layer 38 can be positioned between the inner layer36 and the outer layer 34. The reinforcing braid layer 38 can be formedof any suitable material, including metals and metal alloys. In someembodiments, the reinforcing braid layer 38 can include a metal wirebraid (with wires that are round, flat, or other cross-sectional shape)formed of stainless steel, tungsten, gold, titanium, silver, copper,platinum, or iridium. The reinforcing braid layer 38 can also be formedfrom non-metallic material such as KEVLAR® (poly paraphenyleneterephthalamide) fibers, LCP (liquid crystal polymer) fibers or glassfibers. In some embodiments, the reinforcing braid layer 38 can beformed of a high tensile stainless steel such as 304V stainless steel.In still other embodiments, the reinforcing braid layer 38 can be formedof a polymeric material or polymer blend such as any those disclosedherein.

In some embodiments, the reinforcing braid layer 38 can extend oversubstantially the entire length of the catheter 10. The reinforcingbraid layer 38 can extend from a position proximate to or distal of theproximal end 14 of the elongate shaft 12 to a position proximate to orproximal of the distal end 16 of the elongate shaft 12.

As illustrated, for example, in FIG. 4, a reinforcing braid 42 can beformed of several continuous fibers. In some embodiments, thereinforcing braid 42 can be formed by weaving together two or morecontinuous wires over a mandrel 41. The continuous wires can be flat orround in cross-section and can be woven together in a variety ofpatterns. The reinforcing braid 42 can be formed by weaving together twocontinuous wires 44 and 46, as illustrated.

However, the invention contemplates, for example, using three continuouswires woven together in a three-over-three pattern, while other patternssuch as a four-over-four, two-over-four, or even a five-over-fivepattern can also be used, depending on the number of wires used. Inparticular, the wires can have a round cross section having a diameterof about 1.0 to about 2.0 millimeters. The braid can also be formed withflat or other non-round cross sections. If such a braid is used, thecross section reduces in dimension, such as width and height, versusdiameter for a round wire.

A reinforcing braid 42 can be formed by weaving together two continuouswires 44 and 46 that have cross-sectional diameters that are at leastsubstantially constant from a proximal end 48 of the reinforcing braid42 to a distal end 50 of the reinforcing braid 42. As used herein, acontinuous wire is a single wire that extends from one end of the braidto the other end of the braid, without splicing, welding or any othermeans of joining two wires together. A continuous wire can have aconstant diameter across its entire length. A continuous wire can have adiameter that changes along its length. The diameter can varycontinuously, or the diameter can vary step-wise.

In some embodiments, each of the continuous wires 44, 46 can have thesame diameter. In other embodiments, not illustrated, it is contemplatedthat one continuous wire 44 can have a first constant diameter, whilethe second continuous wire 46 has a second constant diameter that iseither greater or less than the first constant diameter.

Forming a braid 42 from continuous wires 44, 46 of constant diameter canproduce a braid 42 having uniform flexibility, torque transmission andother useful performance parameters. In some embodiments, a braid 42 asillustrated in FIG. 4 can be used in part or all of a catheter 10 andforms the reinforcing braid layer 38 illustrated in the earlier Figures.In some embodiments, the braid 42 can extend from the proximal end 14 ofthe elongate shaft 12 to a point proximal of the distal end 16 of theelongate shaft 12.

In some embodiments, it can be desirable for a portion of the braid 42to be more flexible than another portion of the braid 42. It may beuseful for the distal portion 50 of the braid 42 to be more flexiblethan the proximal portion 48. For example, catheters can have a distalportion 32 that can be curved, as indicated in FIG. 6. In someembodiments, the distal portion 32 can curve in response to anatomicalfeatures encountered in use. In other embodiments, the distal portion 32can be pre-bent or pre-curved prior to use. In order to more easilycurve, it can be useful for any braid present in the distal portion 32to be more flexible.

FIG. 5 illustrates an embodiment of a reinforcing braid 52 that can beformed, as described above with respect to FIG. 4, by weaving togethertwo or more continuous wires 58 and 60 over a mandrel 41. The braid 52shown in FIG. 5 has a proximal portion 54 in which each of thecontinuous wires 58, 60 as a proximal diameter D1 and a distal portion56 in which each of the continuous wires 58, 60 has a distal diameterD2.

In the illustrated embodiment, the distal diameter D2 is less than theproximal diameter D1. In some embodiments, the distal diameter D2 can beabout one-third less than the proximal diameter D1. In a particularembodiment, the proximal diameter D1 can be about 1.5 millimeters, whilethe distal diameter D2 is about 1.0 millimeters. The use of diameter isillustrative of a round wire, although other shaped wire can be usedwith commensurate change in cross-sectional area.

As can be seen in FIG. 6, the reinforcing braid 52 can be positionedwithin a catheter portion 32 such that the proximal portion 54 of thebraid corresponds to a more proximal section 62 of the catheter portion32, while the distal portion 56 of the braid 52 corresponds to a curved,more distal section 64 of the catheter portion 32. As a result, thecatheter portion 32 can be more flexible and supportive. In someembodiments, the reinforcing braid 52 can extend proximally to theproximal end 14 of the elongate shaft 12. In such embodiments, theproximal portion 54 forms the reinforcing braid layer 38.

The reinforcing braid 52 shown in FIG. 6 can be formed in a variety ofways. In some embodiments, the braid 52 can be formed from twocontinuous wires 58, 60, each having equal, constant diameters. Thedistal portion 56 of the braid 52 can then be subjected to a procedurethat will reduce the diameter of the wires 58, 60 within the distalportion 56 of the braid 52. A number of procedures are contemplated,although electro-etching is preferred.

In other embodiments, the braid 52 can be formed from two continuouswires 58, 60 that do not have constant diameters. In particular, each ofthe two continuous wires 58, 60 can be formed having a first portionhaving a first diameter and a second portion having a second, reduceddiameter. The first diameter can correspond to the proximal diameter ofthe continuous wires 58, 60, while the second diameter can correspond tothe distal diameter of the continuous wires 58, 60. The continuous wires58, 60 can have a gradual transition between the first and seconddiameters. The wires 58, 60 can also be formed having a more abrupttransition between the first and second diameters. The wires 58, 60 canbe formed using any of a variety of procedures, although cold-drawing ispreferred.

Once the braid 52 has been formed, it can be incorporated into acatheter 10. An inner layer 36 can be placed on a mandrel. The braid 52can be positioned over the inner layer 36 by axially compressing thebraid 52. This enlarges the inner diameter of the braid 52 and permitseasy positioning of the braid 52 over the inner layer 36. Once the braid52 has been positioned to form the reinforcing braid layer 38, an outerlayer 34 can be installed if desired. The outer layer 34 can beco-extruded over the reinforcing braid layer 38, or it can be pre-formedand then heat shrunk into position.

In at least some embodiments, portions or all of the reinforcing braidlayer 38 can include a radiopaque material. Some examples of radiopaquematerials can include, but are not limited to, gold, platinum,palladium, tantalum, tungsten or tungsten alloy, molybdenum, polymermaterial loaded with a radiopaque filler, and the like.

In some embodiments, a degree of MRI compatibility can be imparted. Forexample, to enhance compatibility with Magnetic Resonance Imaging (MRI)machines, it may be desirable to make the reinforcing braid layer 38, orother portions thereof, in a manner that would impart a degree of MRIcompatibility. For example, the reinforcing braid layer 38 or portionsthereof may be made of a material that does not substantially distortthe image and create substantial artifacts, which are gaps in the image.Certain ferromagnetic materials, for example, may not be suitablebecause they may create artifacts in an MRI image. The reinforcing braidlayer 38 or portions thereof may also be made from a material that theMRI machine can image. Some materials that exhibit these characteristicsinclude, for example, tungsten, Elgiloy, MP35N, nitinol, and the like,and others.

An intravascular catheter 10 can optionally include a coating layer suchas a lubricious coating layer over part or all of the catheter 10.Suitable lubricious polymers are well known in the art and can includehydrophilic polymers such as polyarylene oxides, polyvinylpyrolidones,polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides,caprolactones, and the like, and mixtures and combinations thereof.Hydrophilic polymers may be blended among themselves or with formulatedamounts of water insoluble compounds (including some polymers) to yieldcoatings with suitable lubricity, bonding, and solubility.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of theinvention. The scope of the invention is, of course, defined in thelanguage in which the appended claims are expressed.

1. A catheter shaft, comprising: an elongate shaft member having a proximal end region and a distal end region; wherein the catheter shaft includes a polymer blend having polyoxymethylene dispersed in a blend of polybutylene terephthalate and ether or ester based copolymer; and a catheter braid formed from at least two continuous wires woven together and disposed on the catheter shaft, the catheter braid comprising: a proximal braid section in which each of the continuous wires has a proximal cross-sectional area; and a distal braid section in which each of the continuous wires has a distal cross-sectional area; wherein for each continuous wire, the distal cross-sectional area of said continuous wire is less than the proximal cross-sectional area of said continuous wire.
 2. The catheter shaft of claim 1, wherein the polymer blend includes about 5% to about 40% by volume of polyoxymethylene.
 3. The catheter shaft of claim 2, wherein the polymer blend includes about 5% to about 90% by volume polybutylene terephthalate.
 4. The catheter shaft of claim 2, wherein the polymer blend includes about 5% to about 90% by volume ether or ester based copolymer.
 5. A catheter shaft, comprising: an elongate shaft member having a proximal end region and a distal end region; wherein the catheter shaft includes a polymer blend having polyoxymethylene dispersed in a blend of polybutylene terephthalate and polyether-ester; wherein the shaft member includes a reinforcing braid, the braid having a proximal portion and a distal portion different from the proximal portion.
 6. The catheter shaft of claim 5, wherein the polymer blend includes about 5% to about 40% by volume of polyoxymethylene.
 7. The catheter shaft of claim 5, wherein the polymer blend includes about 5% to about 90% by volume polybutylene terephthalate.
 8. The catheter shaft of claim 5, wherein the polymer blend includes about 5% to about 90% by volume polyether-ester.
 9. The catheter shaft of claim 5, wherein the braid is formed from at least two continuous wires woven together and disposed along the shaft member.
 10. The catheter shaft of claim 9, wherein along the proximal portion of the reinforcement layer each of the continuous wires has a proximal cross-sectional area, wherein along the distal portion of the reinforcement layer each of the continuous wires has a distal cross-sectional area, and wherein for each continuous wire, the distal cross-sectional area of the continuous wire is less than the proximal cross-sectional area of the continuous wire. 